This question is one I've run into a few times recently. It's not
a question I can answer quickly as the question is based on a false
premise about the relationship between lean and agile. So first I
need to go into some history to help explain that relationship.

As regular readers of my work may know, I'm very suspicious of
using metaphors of other professions to reason about software
development. In particular, I believe the engineering metaphor has
done our profession damage - in that it has encouraged the notion of
separating design from construction.

As I was hanging around our London office, this issue came up in
the context of Lean Manufacturing, a metaphor that's used quite
often in agile circles - particularly by the Poppendiecks. If I
don't like metaphoric reasoning from civil engineering, do I like it
more from lean manufacturing?

Canary release is a technique to reduce the risk of
introducing a new software version in production by slowly rolling out the
change to a small subset of users before rolling it out to the entire
infrastructure and making it available to everybody.

One answer for this is to take a sense of proportion. Lean
manufacturing techniques were the underpinning of Toyota's rise from
an insignificant company in the 1950's to a global giant in the
2000's. By the 1990's other car companies, and many other
manufacturers, were busily copying Toyota's techniques. The general
sense is that copying these techniques did much to raise the overall
quality of cars in the last decade or so. I would be very surprised if
the recent problems at Toyota are enough negate that half-century of
success.